Vegetation existing in rivers and floodplains, on the one hand, provides a wide range of ecosystem conditions and, on the other hand, has a significant impact on the increase in the flow resistance that causes a reduction in the flow capacity and in the change in the process of particle sedimentation. Flow resistance (drag coefficient) is an essential parameter for open channels and it has an important impact on biological and engineering calculations. This very research aims at examining the influence of vegetation, as well as some other effective factors, on drag coefficient. Since the choice of shear velocity directly affects the drag coefficient, different approaches are examined to calculate the shear velocity. Also, statistical moments ranging between 1 and 4 are discussed. Finally, for the turning points of shear stress the Bursting process is carried out. In this research, data collection is executed through two means: the field measured and the laboratory part. In the field measured part, a butterfly current-meter was a used to acquire the data on point velocity. 13 cross-sections were measured in which each section included 5 profiles at a vertical position in the flow - two sections were bare bank and 11 sections were with vegetation in the bank. The dominant vegetation on the sides was similar to rice and the bed was of the gravel sort. In the field part, 36 velocity profiles were measured by using the ADV on the slope of 0.5 and 1.5 % – 18 profiles were with vegetation in bank and 18 profiles in bare bank. The results show that the maximum velocity in aspect ratio greater than 5 occurs under the surface of water owing to the vegetation, while the previous studies suggested that the maximum velocity in two dimension currents in aspect ratio greater than 5 is expected to occur on the surface of water. The credibility of log law y/h in vegetation is less than that of the central axis- which points out the existence of vegetation leads to more deviation in the data from the log law. In distribution of shear stress, 3 areas were recognized. Also, different factors such as the vegetation, the change in the slope of the bed, aspect ratio, Froud number, Reynolds number, and Shields parameter have an impact on drag coefficient. Key word: Aspect ratio , Drag coefficient, Flow resistance, Shear velocity, Vegetation